The long-term objective of this proposal is to understand genetics of immune responsiveness. The experimental model of the immune response to alpha (1,3) glycosidic linkages found on B1355 dextran; alpha (1,3) linkages are common environmental epitopes. The specific goal of this project is to determine the molecular basis for the C57B1/6 nonresponder phenotype to the T-cell independent antigen B1355. Hybridomas that produce alpha (1,3) specific antibodies will be prepared by using T-cell dependent antigens and these will be analyzed at the molecular level through DNA recombinant technology. Preliminary data indicate that two types of kappa class and two types of lambda class antibodies are produced by T-cell dependent induction. The types are identified by differential recognition of a synthetic alpha (1,3) glucosyl- protein in ELISA. This contrasts with a single type of low affinity kappa class antibody in response to B1355. The V kappa gene usage of these kappa class antibodies will be identified using specific Vkappa family probes and their relationship to each other will be determined by mRNA sequencing; and their germline counterparts will be identified. The V lambda genes used will likewise be identified using a lambda probe capable of detecting V lambda 1 and V lambda 2 associated with J lambda 1, J lambda 2 or J lambda 3. Whether these are germline V lambda genes will be ascertained by mRNA sequencing. The VH genes used in these responses will be identified by determine family association and primary nucleotide sequences. Comparison of the VH genes used in combination with V lambda with those VH genes of the high responder phenotype will be made to determine the relatedness of the V genes used in high and low responder strains. A comparison of the affinities of the C57B1/6 antibodies will be made with those of BALB/c to aid the understanding of the low responder phenotype. The affinities of the two kappa class and two lambda class antibodies will be studied to determine whether affinity maturation, not normally observed in anti-carbohydrate responses, proceeds via selection of somatic mutants with higher affinity or via the induction of higher affinity B cells expressing unique V genes.